There must be opposites. Consider the trees in Eden: some encouraged, one forbidden; some fruit sweet, other bitter. To “act for themselves” was God’s eternal plan; “to be acted upon” was Satan’s plan.
If only one course were available to us, there would be no choice, no agency. There must be opposites, and that is why two seemingly contradictory commandments were given: “man could not act for himself save it should be that he was enticed by the one or the other.” Choice must always be preserved. If we are forced to do what is right, the choice is not ours, and the principle of obedience is irrelevant.